The invention relates to an apparatus for adjustment of the coating thickness in the coating of traveling webs by means of a doctor roll which bears on the coated side of the web and is supported in a doctor-roll bed that is secured to the machine frame through a mount, said apparatus comprising an inflatable tube between the doctor-roll bed and its mount.
An apparatus of this type is known from German patent application DOS No. 23 07 404, for example. The doctor-roll bed in that apparatus is made of a resilient material such as plastic or the like, and the tube which is inflated pneumatically is disposed as a separate part between the doctor-roll bed and the machine frame. Adjustment of the thickness in which the coating is applied, and hence metering of the coating material, are effected through variation of the pressure in the inflatable tube, the doctor roll being pressed against the web to be coated with greater or less pressure. The accuracy of adjustment is greatly affected by the ease with which the doctor-roll bed moves relative to its mount as the pressure in the inflatable tube is changed.